Process for recovery of oil from shale



Aug. 12, 1958 J.. STEWART ET AL FROOEss FOR RECOVERY OF OIL FROM sHALE AFiled July 1, v1955 mefm #Zwam a m .d n n w m H n d@ nr f e mmmm w.u.a`6.1- HW h r 0U @why SeTB otr JSA nited States *i aterit Zdbd PatentedAug. l2, i958 2,847,306 rnocnss Fon nacovnur or on. FROM SHALE .losephStewart, Cranford, Stewart C. Fulton, Elizabeth, and Arthur W. Langer,Jr., Nixon, N. J., assignors to Esso Research and Engineering Company, acorporation of Delaware Application .luly 1, 1953, Serial No. 365,343

v 1 Claim. (Cl. 196'14) The present invention relates to an improvedprocess for the recovery of oil from shale and from analogous minerals.lt pertains more particularly to a process by which oil may be recoveredor extracted from shale and other minerals by a hydrogen donor action.

As particularly described in a concurrently tiled application by Langer,one of thepresent inventors, Serial No. 365,335, now abandoned, it hasbeen found that various oil residua which are relatively low in hydrogencontent may be upgraded by treating them with certain types of partiallyhydrogenated condensed ring aromatic fractions. The present invention isrelated to that just mentioned but is distinguished therefrom in itsapplication to oil shale. Gil shale, so-called, ordinarily does notcontain oil as such but contains rather a solid organic predominantlyhydrocarbon material known as kerogen. in conventional processes, acrude oil is obtained from shale by retorting. This crude oil is thenfurther refined by distillation, cracking, etc., to obtain the desiredoil products. The shale is usually subdivided into small particles andheated for a prolonged period so as to crack the kerogen into liquidoil. The temperature for retorting is usually around 800 to 1000 F. Atthis temperature, in conventional retorting, a substantial part of thekerogen is converted to coke which remains in situ in the shale residue.Hence, a substantial part of the potential oil yield is lost. For thisreason, among others, the recovery of oil from shale by retorting hasnot been economically attractive.

The prior art has also proposed to recover oil from shale by highpressure hydrogenation. The cost of large scale high pressure equipmentalone is such as to make this process unattractive, aside from the costof hydrogen, problems of hydrogenation catalyst contamination, etc.

According to the present invention practically all of the organicmaterial in oil shale is recovered in a useful form. A liquid diluent,which is also a hydrogen donor, is heated with subdivided shale toconvert most of the kerogen to liquid oil, in situ. The diluent-donorextracts the liquid oil as it is formed and substantially totalconversion of the kerogen to oil takes place with comparatively littlecoke formation. Such carbonaceous material as remains in the shale isrecovered as CO and utilized as described below.

A particular feature of the invention is the choice of a veryinexpensive yet highly effective donor material. While the prior art hassuggested the use of certain chemicals of comparatively very high costfor use as hydrogen donor materials in some types of hydrocarbonconversions, these have not gone into commercial use. According to thepresent invention, a partially hydrogenated highly aromatic oilfraction, such as thermal tar from petroleum catalytic cracker bottoms,is a preferred donor diluent. It may have a boiling range between about500 and 950 F., or two fractions, one of boiling range of about 600 to950 F. and the other of a somewhat lower range, e. g. 500 to 750 F., maybe used sequentially. The rst is mixed with the shale in a slurry tankor drum, under pressure of 200 to 500 p. s. i. g. or more. The slurry ispassed into a soaker drum or series of drums where heating is continuedfor about 0.5 to l0 hours at a temperature within the range of about 700to 950 F., preferably 750 to 900 F. lt is preferred usually that not allof the diluent be added in the slurry tank, a portion, preferably oflower boiling range, being added to the soaker at reaction temperature.This portion preferably is of lower boiling range so as to diffuse morerapidly into the shale and thereby remove the oil more effectively. Thetotal amount of donordiluent should be about 5 to l5 times the weight ofthe kerogen in the shale.

The extracted shale, which settles to the bottom of the soaker tank ortanks, is removed therefrom after the desired soaking period and passedinto a reactor vessel. Here it is lluidized by passing steam upwardlythrough it. The steam strips out essentially all of the diluent and mostof the kerogen, now converted to a liquid oil. The oil phase from thestripper is taken to a fractionator. The hot dried shale residue, whichstill contains a small amount of carbonaceous matter, is taken to asecond reactor, preferably of the iluid bed type, where it is contactedwith an oxidizing gas to form carbon monoxide. Here it is furtherheated, by the combustion process, to a temperature of about 1000 to1200 F. The carbon monoxide is reformed by the well known water gasreaction to produce hydrogen and CO2. The C02 is scrubbed out byconventional alkaline reactants such as ethanolamine or the like and theproduct hydrogen is used to hydrogenate the donor diluent.

The donor-diluent, introduced originally from an extraneous source, islargely recycled and rehydrogenated so that requirements for continuousor periodic addition of extraneous material are minimized. Hydrogenationof the donor diluent is accomplished in a conventional manner, usingmoderate pressures and a suitable hydrogenation catalyst. Although anyresidual CO in the hydrogen may be removed, e. g. by scrubbing withammoniacal cuprous sulfate, so as to avoid contamination of thehydrogenation catalyst, it is usually preferred to use an insensitivecatalyst such as molybdenum sulfide which is not subject to poisoningeither by CO or by the sulfur content of the donor-diluent to behydrogenated. In this Way, removal of the CO becomes unnecessary.

The hot spent shale, now substantially free of all organic matter, isdischarged through a heat exchanger to recover its sensible heat,preferably for generation of required steam for the process, althoughthe heat may be used for other purposes.

The invention will be more fully understood oy reference to a specificembodiment illustrated diagrammati cally in the attached drawing whichforms a part of this specification.

In the drawing, shale which is crushed to small particles, e. g. lessthan one inch and preferably less than onequarter inch in averagediameter, is fed to a hopper or slurry tank 11. The crushing operationis conventional and need not be illustrated. A liquid oil fraction,referred to hereafter as a diluent, hydrogen donor, or donor-diluent, isfed into tank 11 from a line 13 to form a slurry.

The slurry is passed through a line 15 and through a preheating coil i7,heated in any appropriate manner, into the soaking or extractor drum 19.Here the slurry is kept at a temperature within the range of 700 to 950F., preferably between 750 and 900 F., for a period of time sucient toconvert substantially all of the kerogen to liquid oil and to extract itfrom the shale. The time required is ordinarily between 0.5 and l0hours. During this period of time, the hydrogen donor diluent not onlyadds hydrogen to the cracked kerogen to form liquid oil in situ in theshale but it also acts as a solvent to extract the oil as it is formed.The slurry is kept agitated in vessel 19 but the shale is graduallysettled out and conveyed through a line 21, preferably by gravity, to astripping zone The oil phase is taken out above the settling shalethrough a line 23. The oil and shale are preferably under pressure of100 to 1000 p. s. i. g. in this vessel, a pressure above 250 p. s. i. g.being preferred.

The amount of donor-diluent employed may vary somewhat with types ofshale, ineness of subdivision, and heating temperatures. in general, thetotal weight of diluent will be from to 15 times the weight of thekerogen content of the shale. Thus with a shale running 1 barrel of oilper ton, 5 to 15 barrels of donor-diluent will be used to slurry eachton of shale. The hydrogen donor requirements in such large quantitiesof diluent are relatively very low, about 20 to 500 s. c. f. per barrelof diluent, as compared with 200 to 2000 in hydrogen donor diluentcracking (HDDC) of petroleum residua, as described in the copendingapplication mentioned at the beginning of this specification. Henceoverall hydrogen requirements are moderate.

The shale is taken into a stripper where it is fluidized and strippedwith steam fed in at 27. Fluidization of the shale is not alwaysnecessary but is preferred. The steam, at a temperature comparable withthat of the shale or a little higher, 750 to l000 F., removessubstantially all of the diluent and nearly all of the other organicmatter. A small amount, however, remains with the shale. The shale isthen passed to a burner 29 through line 31.

The stripped vapors from the fluidized shale in vessel 25 are taken outthrough a line 33 through suitable solids separating means such as aconventional cyclone (not shown) to a heat exchanger 35 and a condenser37 where the condensed steam is withdrawn. The oil layer passes througha line 39 to join the oil phase in line 23 to a fractionator 41.

ln fraetionator 41 the oil plus spent diluentis fractionated,appropriate side streams being provided for gas, gasoline, light gasoil, diluent and heavy gas oil, as in dicated at 43, 45, 47, 49 and :71.The diluent fraction, boiling preferably between about 600 and 900 F.,though other fractions may be used as previously mentioned, is takenthrough line S3 to a hydrogenator 55. To maintain the aromaticity of thefraction and retain ease of hydrogenation, a small portion is preferablypurged through a line 57, and a similar quantity of thermal tar is addedthrough line 9S.

The bottoms from fractionator 41 is recycled through aline 59 to joinwith recycled hydrogen donor diluent to the slurry tank 11. A portion ofthis fraction may be purged to prevent undue build-up of objectionableconstituents through a line 61.

in burner 29 air or oxygen, preferably air, is admitted through a line65 at such a rate as to convert the carbon in the shale residue tocarbon monoxide and to heat the residue to a temperature within therange of about 1000 to 1200 F. This air may also be used to uidize theshale in burner 29, auxiliary lluidizing gas being introduced atappropriate points (not shown) if needed, as will be obvious. The spentshale is then withdrawn through a line 67 after recovery of its heat forthe generation of steam for stripping in line 27, steam for reactingwith the carbon monoxide, etc.

The carbon monoxide gas from the spent shale passes overhead through aline 69 into a hydrogen producer vessel 71. Steam is supplied to thisvessel through a line 73. The reaction produces a mixture of carbondioxide and hydrogen which passes through line 75 into a scrubber 77where the carbon dioxide is removed.

The scrubbed hydrogen gas which is now fairly pure, containing usuallyaround 1 to 2% of CO, passes through a line 81 into the hydrogenator 55.Here, under appro- '4 priate hydrogenation conditions, e. g. a `pressureof 250 to 2000 p. s. i. g. and in the presence of a suitable catalystsuch as molybdenum sulde, the diluent fraction is mildly hydrogenated.

The gases which pass overhead from the hydrogenator S5 may be purged at83, a substantial portion, however, being recycled through a line 85.The now partially hydrogenated donor diluent passes through a line 87,89 to recycle into line 13 and to slurry tank 11. A portion of thisdonor diluent is fed into the soaker or extractor 19 through a line 91.Usually one-third to two-thirds of the donor diluent is used in theslurry tank and the remainder in the soaker extractor 19.

As mentioned above, a lower boiling portion of donor diluent may be usedin the extractor and this may be derived from an extraneous source orfrom a separate fraction if desired. A line 93 is provided for thispurpose, appropriate control valves (not shown) being provided also aswill be obvious.

It will readily be apparent to those skilled in the art that variousother modifications may be made without departing from the spirit of theinvention.

What is claimed is:

A process for recovering and converting oils from oil shale whichcomprises subdividing the oil shale into small particles, forming aslurry of the subdivided oil shale particles with a partiallyhydrogenated thermal tar, said thermal tar having been obtained asbottoms from a catalytic cracking operation, said partially hydrogenatedthermal tar having a boiling point in the range between about 600 and950 F., heating the slurry to a temperature between about 750 and 950 F.and passing the heated slurry to a soaking Zone wherein it is maintainedat a temperature between about 750 and 950 F. for a time between about0.5 and 10 hours and under a pressure of at least 200 p. s. i. g.,adding partially hydrogenated thermal tar lower boiling than saidfirst-mentioned partially hydrogenated thermal tar to the slurry in saidsoaking zone, said second-mentioned partially hydrogenated thermal tarhaving a boiling range between about 500 and 750 F., whereby oil isextracted from the subdivided oil shale particles by the solvent actionof said partially hydrogenated thermal tar fractions and hydrogen istransferred from the partially hydrogenated thermal tar fractions tosaid oil, the total amount of partially hydrogenated thermal tar usedbeing in the range of about 5 to 15 parts by weight based on the weightof kerogen in the oil shale, separating an oil phase from spent shaleparticles by settling, 'treating the oil phase to recover oil productsand a spent thermal tar fraction for reuse in the process, passing thespent shale particles to a stripping zone," stripping the spent shaleparticles in said stripping Zone to recover oil from the spent shaleparticles and burning the stripped shale particles to provide heat forat least part of the process.

References Cited in the le of this patent UNITED STATES PATENTS1,711,499 Hofsass May 7, 1929 1,794,865 Pier et al. Mar. 3, 19312,147,753 Pott et al. Feb. 2l, 1939 2,322,863 Marschner et al. June 29,1943 2,426,929 Greensfelder Sept. 2, 1947 2,467,920 Voge et al Apr. 19,1949 2,502,958 Johnson Apr. 4, 1950 2,587,729 Huff Mar. 4, 19522,601,257 Buchan June 24, 1952 2,614,067 Reed et al. Oct. 14, 19522,658,861 Pevere et al. Nov. 10, 1953 OTHER REFERENCES Hodgman et al.:Handbook of Chemistry and Physics, 35th ed., pages 732 and 733, publ. byChemical Rubber Publishing Co., Cleveland, Ohio (1953).

